In the removal of the enamel shell which protects the underlying structure, the more permeable dentin is exposed to thus render the remaining tooth structure more susceptible to dental decay as well as creating an entrance for harmful stimuli to the vital pulp beneath.
A common practice prior to restoring the missing structure with a filling material or cement is to apply a thin layer of cavity varnish over the entire exposed dentin area in order to (1) provide a barrier to moisture penetration, (2) serve as insulation against external stimuli, and (3) reduce marginal leakage around a restoration.
Cavity preparation generates extensive microundercuts throughout the cavity walls. These microundercuts serve to promote good retention of a closely packed restoration. In order to benefit from these microundercuts, a cavity varnish should precisely conform to each "peak" and "valley" of the microundercuts with no concomitant loss of definition thereof caused by the varnish. Thus, the varnish must be capable of fully wetting the dentin surfaces while spreading uniformly over their general topography, and yet not swamping the microundercuts. Conventional cavity varnishes have been only mildly successful in fulfilling the above requirements.
Additionally, a dental cavity varnish should be compatible with composite resin restorative materials, such as bisphenol-A resin, for example, currently in wide usage by the dental profession.
It is well known that composite materials can irritate underlying tooth structures. The use of a protective varnish therefore is appropriate. Unfortunately, traditional varnishes were developed, in the main, for compatible use with amalgams and silicates, both widely used prior to composite resin restorative materials. For example, a widely used prior art copal-containing cavity varnish caused an unpolymerized mushy layer to form when the composite was applied over the varnish film. This unreacted layer permitted ready access to the dentin area, or seepage thereinto, of harmful stimuli.
The present invention substantially satisfies the abovementioned requirements, i.e., complete wetting of the dentin surfaces while providing a thin but uniform film over the microundercuts without obstructing the peaks and valleys thereof; and complete compatibility with composite resin restorative materials, as well as amalgams and silicates. In addition thereto, the present varnish is fast drying, hydrophobic when dry, simple to use, and possesses long shelf life and good sealing ability .